Cancer is a serious health problem throughout the world. As a result, an extensive amount of research has been conducted to develop therapies appropriate to the treatment and alleviation of cancer in humans.
In the chemotherapeutic area, research has been conducted to develop anti-tumor agents effective against various types of cancer. Often anti-tumor agents developed and found effective against cancerous cells, unfortunately, are toxic to normal cells. This toxicity gives rise to hair loss, nausea, weight loss, vomiting, hallucination, fatigue, itching, loss of appetite, etc., when administered to a patient needing cancer therapy.
Further, conventionally used chemotherapeutic agents do not have the effectiveness desired or are not as broadly effective against different types of cancers as is desired. As a result, chemotherapeutic agents which have greater effectiveness against cancers and which have a higher degree of selectivity for killing cancer cells with no or minimal effect on normal healthy cells is desired. Highly effective and selective anti-tumor agents, in particular, against cancers of the colon, bladder, prostate, stomach, pancreas, breast, lung, liver, brain, testis, ovary, cervix, skin, vulva, small intestine and like organs is desired. Anti-tumor agents against cancers such as colon cancer and melanomas are also particularly desired because of the lack of any particularly effective therapy at present.
Certain types of cyanine dyes have been disclosed as having anti-cancer activity (see, for example, Japanese Kokai 79/151,133, 80/31,022, 80/69,513, 80/100,318, Japanese Koho 89/52,325, E.P. No. 286252A2). However, these cyanine dyes cannot be used effectively for therapy in humans because of their high toxicity to healthy cells as well as to cancer cells. In addition, these cyanine dyes often are poorly soluble in diluents acceptable for human administration.
Furthermore, a solution of drug having an absorption at short wavelength, i.e., the solution of light color is preferably acceptable in medical and pharmaceutical fields and the like since it does not cause patient a feeling of uneasiness rather than a solution of dark color does. In this connection, certain rhodacyanine dyes have high toxicity to cancer cells and low toxicity to normal cells, but the dyes are not satisfactory in terms of absorption at short wavelength, and as a result, it is desired to have a solution of drug having an absorption at shorter wavelength.